1. Field of the Invention
This invention relates generally to conveyor systems for articles such as printings. More particularly, the invention deals with a conveyor system to be appended to a web-fed printing press, in a position immediately downstream of the delivery fan, for transporting the completed printings, known to the specialists as signatures, to a subsequent processing station such as a stacking station.
2. Description of the Prior Art
Japanese Patent No. 3,046,308 teaches an integrated conveyor system for transporting signatures from a web folding and cutting station to a stacking station, with or without use of the delivery fan which is customarily employed for depositing the signatures from the folding and cutting station onto the conveyor one by one. This known conveyor system is in essence an endless chain with sets of wheels mounted to the chain links to roll along a looped guide rail. Each chain link is additionally furnished with a cooperative pair of grip fingers which open to receive an edge of a signature issuing from the folding and cutting station, which close to grip and carry the signature, and which reopen at the stacking station to release the signature.
This prior art chain conveyor had a weakness which manifested itself in the event of a jam of the signatures, particularly in the neighborhood of where the signatures were loaded on the conveyor by being gripped by the grip fingers. Being constituted of a single endless chain, the complete conveyor had to be set out of operation pending the system recovery from the trouble. All the signatures that had been being carried then by the endless chain conveyor had to be held at a standstill, blocked against further processing, until the conveyor resumed operation.
Japanese Unexamined Patent Publication No. 2000-103,557 suggests a conveyor system that incorporates two successive endless chain conveyors in order to defeat the weakness above. Both chain conveyors have gripping devices mounted to their links for engaging and carrying the signatures. The signatures are first loaded onto a first chain conveyor and thence onto a second chain conveyor for transportation to the subsequent processing station. The second chain conveyor has two endless chains parallel to each other, each carrying a row of gripping devices. At the junction between the first and the second chain conveyors, the two rows of gripping devices on the second lie on both sides of the row of gripping devices on the first. A belt conveyor is additionally provided for supporting the free edges of the signatures being carried by the first chain conveyor.
Only the first chain conveyor needs to be stopped in event a jam occurs at its loading end or upstream in this second prior art device. The signatures that have been carried by the second chain conveyor at that time can all be conveyed to the next station for continued processing.
The second prior art device has its own shortcomings. During transfer from the first to the second chain conveyor, the pair of gripping devices of the second conveyor are intended to engage the signature at its edge parts on both sides of where it is gripped by the first conveyor. However, as such edge parts are easy to sag while the signature is being carried by the first conveyor, the pair of gripping devices of the second conveyor sometimes failed to engage, or failed to engage correctly, the required edge parts of the signature. Then the signature either fell off the conveyor system or was ruined in the course of further processing. Human labor was required for recovery and disposal of such waste printings. The noted belt conveyor was incapable of totally eliminating such sagging of the signatures and, what is worse, itself added to the bulk of the printing system.